LHCB RICH pattern recognition and particle identification performance

The RICH system of LHCb will provide the hadron identification which is essential for the physics aims of the experiment, namely to fully reconstruct very rare B-hadron decays and study CP violation. Two RICH detectors, making use of three radiators, aerogel, C 4 F 10 and CF 4 gases, will provide pion–kaon separation over the momentum range from about 1 to 100 GeV/c. The high multiplicity environment of the LHC means that a high performance pattern-recognition algorithm is crucial for achieving this aim. Such an algorithm, using a global likelihood approach, has been developed for the RICH offline reconstruction. In addition, a faster pattern recognition algorithm has been devised, suitable for use in the LHCb High Level Trigger. The concepts which underpin both approaches will be described, and the performance will be shown in terms of identification efficiency and misidentification fraction as a function of track momentum.